Pointer, position detection apparatus and position detection method

ABSTRACT

A position detection apparatus of the electrostatic coupling type is provided, to detect not only a position of a pointer but also information other than the position information such as, for example, pointer pressure or side switch information. The pointer transmits two codes such that a pressure applied to a pen tip is associated with a time difference between the two codes. A position detector carries out a correlation matching operation between signals generated in reception conductors and correlation calculation codes corresponding to the two codes, to thereby detect a position on a sensor section pointed to by the pointer from a result of the correlation matching operation and based on at least one of the codes. The position detector further includes a pressure calculation circuit for detecting pressure applied to the pointer, which is associated with the time difference between the two codes, from the result of the correlation matching operation calculated by the correlation matching operation and based on the two codes.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit under 35 U.S.C. §119(a) ofJapanese Application No. 2010-024858, filed Feb. 5, 2010, the entirecontent of which is incorporated herein by reference.

TECHNICAL FIELD

This invention relates to a pointer, a position detection apparatus anda position detection method, and more particularly to a pointer, aposition detection apparatus and a position detection method of theelectrostatic coupling type.

BACKGROUND ART

A position detection apparatus, called a tablet, has been developed asone of pointing devices used for producing an image or illustration on acomputer apparatus. Such a position detection apparatus typicallyincludes a position detector substantially in the form of a flat plate,and a pointer in the form of a pen to be operated by a user on theposition detector.

As such a position detection apparatus, for example, a positiondetection apparatus based on an electrostatic coupling method has beendeveloped. The position detection apparatus of the electrostaticcoupling type includes, as principal components thereof, a pointerincluding an integrated circuit (IC) and a position detector including asensor section having a group of conductors arrayed in a predeterminedpattern. A predetermined signal is transmitted from the pointer, whichis placed on the sensor section, to the conductor group, and theposition pointed to by the pointer is detected by specifying thereception position of the transmission signal by the position detector.

A conventional position detection apparatus is described, for example,in Japanese Patent Laid-Open No. H8-50535.

SUMMARY OF THE INVENTION

In the position detection apparatus of the electrostatic coupling type,typically, a signal transmitted from the pointer to the sensor sectionis used to detect the position pointed to by the pointer. Therefore,such a position detection apparatus has a problem that, although it ispossible to detect the position pointed to by the pointer, it cannotdetect information other than the position information such as, forexample, the pointer's pressure information (i.e., how much pressure isapplied to the pointer tip by a surface of the sensor section) or pendown information, which indicates that the pointer is in contact withthe position detector. Also, there is a problem that a plurality ofdifferent pointers, such as a pointer in the form of a pen and a fingeras a pointer, cannot be detected at the same time.

According to one aspect, the present invention is directed to solvingthe problems described above. According to an aspect of the presentinvention, a position detection apparatus is provided, which adopts theelectrostatic coupling method to detect, through use of codes for whicha correlation matching operation process is carried out, not onlyposition information representative of the position pointed to by apointer but also information other than the position information suchas, for example, pressure information, information of a rotationalposition where the pointer is rotated on a position detector around apen tip (axis) thereof, or information regarding inclination of thepointer. Further, according to another aspect, the present inventionmakes it possible to detect information from a plurality of differentpointers, such as position pointing information by a pen and a finger asa pointer, at the same time.

According to one aspect of the present invention, there is provided aposition detection apparatus including a pointer having a transmissionsignal production section, which produces a signal based on two codessuch that a pressure applied to the pointer is associated with a timedifference between the two codes. The pointer transmits the signalproduced by the transmission signal production section. The positiondetection apparatus further includes a sensor section having a pluralityof first conductors disposed in a predetermined direction and aplurality of second conductors disposed in a direction crossing with thepredetermined direction. The sensor section is configured to receive thesignal transmitted from the pointer. The position detection apparatusfurther includes a correlation matching operation circuit configured tocarry out a correlation matching operation between signals generated inconductors which form the plurality of first conductors and theplurality of second conductors and correlation calculation codescorresponding to the two codes. The position detection apparatus stillfurther includes a position calculation circuit configured to detect aposition on the sensor section pointed to by the pointer based on aresult of the correlation matching operation calculated by thecorrelation matching operation circuit and based on at least one of thecodes. The position detection apparatus also includes a pressurecalculation circuit configured to detect the pressure applied to thepointer, which is associated with the time difference between the twocodes, based on the result of the correlation matching operationcalculated by the correlation matching operation circuit and based onthe two codes. Further, in order to detect information other than theposition information, such as the rotational position, where the pointeris rotated around a pen tip (axis) thereof on a position detector, orthe inclination of the pointer, a plurality of electrode pieces dividedelectrically from each other are disposed around the central axis of thepointer on the pointer, and codes of different types are suppliedrespectively to the plurality of electrode pieces. Further, in order todetect a pointing operation by a finger simultaneously with a pointingoperation by a pen, the position detector may further include a codeproduction section and a changeover (switching) section for switchingthe conductors, which form the sensor section, between signal receptionand signal transmission.

It is to be noted that the two codes described above may have the samecode pattern or may have code patterns different from each other. Wherethe same code pattern is used, the same correlation calculation codecorresponding to the code pattern can be used.

According to another aspect of the invention, a pointer is provided,including an end portion (pen tip) for pointing to a position. The endportion projects from a housing. The pointer also includes a codeproduction circuit configured to produce a first code and a second codehaving code patterns different from each other and to control, inresponse to a pressure applied to the end portion of the pointer, theproduction timings at which the two codes are to be produced, that is, atime difference between the codes. Alternatively, the code productioncircuit is configured to produce one code having a predetermined codepattern and to control, in response to a pressure applied to the endportion of the pointer, the timing for next production of the coderelative to the first production of the code, that is, a time differencebetween the codes. The pointer may also include a transmission signalproduction section configured to transmit the codes produced by the codeproduction circuit.

Various exemplary embodiments of the present invention are suited wherean electrostatic coupling method is used to form a position detectionapparatus. First and second codes having the same code pattern or havingcode patterns different from each other are transmitted from a pointer,with a time difference therebetween, and received by a positiondetector. Then, position detection of the pointer is carried out usingthe first code, while information other than the position information,such as pressure information or rotational position information of thepointer, is obtained based on the time difference between the two codes.

As described above, with exemplary embodiments of the present invention,the first code and the second code having code patterns that are thesame as each other or different from each other are transmitted from thepointer and, upon signal reception, a correlation matching operationbetween the reception signal and correlation calculation codes thatrespectively correspond to the first and second codes is carried out.Accordingly, not only the pointing position of the pointer but alsoinformation other than the position information such as, for example,pressure information can be detected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a position detection apparatus accordingto an embodiment of the present invention.

FIG. 2 is a view of a general configuration of a pointer according to anembodiment of the present invention.

FIGS. 3A and 3B are circuit block diagrams of a transmission codeproduction section in the pointer.

FIG. 4 is a view of a general configuration of a position detectoraccording to an embodiment of the present invention.

FIG. 5 is a view of a general configuration of a correlation matchingsection.

FIG. 6 is a view of a general configuration of a correlator.

FIGS. 7A-7C are views illustrating operation of the correlator.

FIG. 8 is a flow chart illustrating an operation procedure of thepointer.

FIG. 9 is a flow chart illustrating an operation procedure of theposition detector.

FIGS. 10A-10C are views illustrating a principle of position detectionand pressure detection of the pointer, where first and second codes aretransmitted in a time-multiplexed state.

FIG. 11 is a view of a general configuration of a pointer ofmodification 1.

FIGS. 12A and 12B are views of a general configuration of a pointer ofmodification 2.

FIG. 13A is a waveform diagram of a code, before PSK modulation, andFIG. 13B is a signal waveform diagram of the code after the PSKmodulation, which forms a signal to be transmitted from a pointer ofmodification 3.

FIG. 14 is a view of a general configuration of a pointer of themodification 3.

FIG. 15 is a view of a general configuration of a reception systemcircuit group of a position detector of the modification 3.

FIG. 16A is a waveform diagram of a code, before FSK modulation, andFIG. 16B is a signal waveform diagram of the code after the FSKmodulation, which forms a signal to be transmitted from a pointer ofmodification 4.

FIG. 17 is a view of a general configuration of a pointer of themodification 4.

FIG. 18 is a view of a general configuration of a reception systemcircuit group of a position detector of the modification 4.

FIG. 19 is a view illustrating rotation detection and inclinationdetection of a pointer of modification 5

FIG. 20 is a view of a general configuration of a pointer of themodification 5.

FIG. 21 is a view of a general configuration of a position detector ofmodification 6.

FIG. 22 is a view of a general configuration of a position detector ofmodification 7.

FIG. 23 is a view illustrating operation of the position detector of themodification 7.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

An embodiment of a position detection apparatus of the present inventionis described with reference to the drawings. However, the presentinvention is not limited to the following embodiment.

In the present embodiment, two codes having code patterns different fromeach other or two codes having the same code pattern are used to detectthe position of a pointer and pressure of the pointer, that is, pressureapplied to the pointer. If the code to be used is, for example, an 8-bitcode, then one or a plurality of code patterns are used as selected fromamong “11110000,” “11001100” and “10101010.” Also, code patterns of“00101101,” “11001100” and “10101010” can be used.

If those code patterns are used, then the code patterns can beidentified by a correlation matching operation upon reception. As othercodes, for example, spread codes including an M sequence, a gold codesequence or the like or orthogonal codes such as, for example, theHadamard code or the Walsh code may be used. It is to be noted that,where an orthogonal code is used, the identification sensitivity of codepatterns can be increased based on a correlation matching operationprocess upon reception.

[Configuration of the Position Detection Apparatus]

FIG. 1 shows a perspective view of the position detection apparatus ofthe present embodiment. It is to be noted that, in the presentembodiment described below, a tablet is used as the position detectionapparatus. The position detection apparatus 1 includes a pointer 2having a shape of a pen, and a position detector 3 having a shape of aflat plate and being connected to an external apparatus such as apersonal computer (PC) through an external apparatus connecting cable 4

The pointer 2 is used on a scannable region 3 a of the position detector3. On the scannable region 3 a, a pointed position (coordinate),pressure, and so forth of the pointer 2 can be detected by the positiondetector 3.

The position detector 3 detects the coordinate of a position pointed toby the pointer 2 and outputs the coordinate information to the externalapparatus. Then, on a display screen (not shown) of the externalapparatus, a pointer or the like is displayed at a positioncorresponding to the coordinate information inputted from the positiondetector 3.

[Configuration of the Pointer]

FIG. 2 shows a general configuration of the pointer 2 of the presentembodiment. The pointer 2 includes a first electrode 20, a secondelectrode 21, a variable capacitor 22, an integrated circuit 23, a coil24, a power production circuit 25, and a housing 129 which accommodatesthe above-mentioned components therein. The variable capacitor 22 is acapacitor that varies its capacitance value in response to a pressureapplied thereto. The housing 129 is formed from a material havingconductivity such as a metal.

The first electrode 20 has a shape of a rod and is disposed such thatone end portion thereof projects from one end portion of the housing129. Further, the projecting end portion of the first electrode 20 hasconductivity and functions as a pen tip. In particular, the end portionprojecting from the housing 129 functions as a pen tip of the pointer 2and functions also as the first electrode 20. Meanwhile, the secondelectrode 21 is, in the present example, a substantially cylindricalelectrode and is disposed in such a manner as to surround the firstelectrode 20. In particular, the second electrode 21 is disposed alongan inner peripheral face of the housing 129 around the first electrode20 having a shape of a rod. Further, codes (C1 and C2) outputted fromthe integrated circuit 23 are added together through resistors (R1 andR2) and then supplied to the first electrode 20 and the second electrode21. Accordingly, the signals outputted from the integrated circuit 23,which respectively correspond to the two code patterns, are applied in amutually added state to the first electrode 20 and the second electrode21 so that signals are transmitted to the position detector 3 throughthe first electrode 20 and the second electrode 21.

The variable capacitor 22 disposed as a pressure detection element has aconfiguration that the capacitance thereof varies in response to apressure (so-called “pen pressure”) applied to the pen tip. Inparticular, the variable capacitor 22 is configured such that one of apair of electrodes (not shown) which form the variable capacitor 22 isengaged with an end portion of the first electrode 20. Therefore, if thepointer 2 is brought into contact with the position detector 3 to pressthe first electrode 20 on the scannable region 3 a, then also the oneelectrode of the variable capacitor 22 is pressed. Consequently, anelectric characteristic between the paired electrodes of the variablecapacitor 22 varies to change the capacitance of the capacitor. In otherwords, the capacitance variation amount of the variable capacitor 22corresponds to the pressure. It is to be noted that a variableinductance coil configured such that the inductance thereof varies inresponse to the pressure or a variable resistor configured such that theresistance value thereof varies in response to the pressure may be usedas the pressure detection element. Further, a resonance circuitincluding one of a variable capacitor, a variable inductance coil, and avariable resistor may be used. In short, it is only necessary for thepressure detection element to have a configuration such that pressure(pen pressure) applied to an end portion (pen tip) of the pointer 2 actsupon a production starting timing of a code signal outputted from atransmission code production section 28.

The transmission code production section 28 including a first codeproduction section 26 and a second code production section 27 forms theintegrated circuit 23. In the present embodiment, a first code C1outputted from the first code production section 26 is used to carry outposition detection while the first code C1 as well as a second code C2outputted from the second code production section 27 are used to carryout pressure detection.

Output terminals of the integrated circuit 23 are connected, throughresistors (R1 and R2), to the first electrode 20 and the secondelectrode 21, so as to output a transmission signal corresponding to thefirst code C1 and/or the second code C2 to the first electrode 20 andthe second electrode 21 at a predetermined timing. It is assumed that,in the present embodiment, the first code C1 outputted from the firstcode production section 26 and the second code C2 outputted from thesecond code production section 27 have code patterns different from eachother. However, the present invention is not limited to thisconfiguration, and the same code pattern may be used to produce twocodes by controlling the signal production starting timings of thesecodes, as hereinafter described.

The second code production section 27 is connected to the variablecapacitor 22. Further, the second code production section 27 varies thesignal production starting timing of the second code C2 based on acapacitance variation of the variable capacitor 22 according to the penpressure. In particular, in the present embodiment, the time differencebetween the production timing of the first code C1 outputted from thefirst code production section 26 and the production timing of the secondcode C2 corresponds to the pressure applied to the pointer 2.

The integrated circuit 23 includes a control circuit (not shown) forcontrolling operation of the transmission code production section 28,and a clock signal and other signals necessary for the control areproduced by the control circuit. It is to be noted that the integratedcircuit 23 is driven by a voltage produced by the coil 24 and the powerproduction circuit 25 hereinafter described.

The coil 24 receives an excitation signal signaled from an excitationcoil 35 of a sensor section 30 hereinafter described provided in theposition detector 3. Consequently, a high frequency signal is induced inthe coil 24. The induced high frequency signal is inputted to the powerproduction circuit 25. The power production circuit 25 has arectification circuit not shown and rectifies the high frequency signalsupplied from the coil 24 by means of the rectification circuit toconvert the high frequency signal into a DC voltage. Then, the powerproduction circuit 25 supplies the DC voltage obtained by theconversion, as driving power for the integrated circuit 23, to theintegrated circuit 23.

It is to be noted that, while, in the present embodiment, the first codeproduction section 26 and the second code production section 27 forproducing the first code C1 and the second code C2, respectively, areprovided in the integrated circuit 23, the present invention is notlimited to this configuration. Another configuration may be usedwherein, for example, a ROM (Read Only Memory) is provided in theintegrated circuit 23 and the first code C1 and the second code C2 arestored in the ROM such that, when transmitting codes, the code patternsare read out from the ROM and transmitted. It is to be noted that, inthis instance, a corresponding relationship between the capacitancevariation amount ΔC of the variable capacitor 22 and the signalproduction starting timing of the first code C1 and the signalproduction starting timing of the second code C2 is prestored as a tablein the ROM.

FIGS. 3A and 3B show examples of a circuit configuration of thetransmission code production section 28 in the pointer 2 shown in FIG.2. FIG. 3A shows an example of a circuit configuration of thetransmission code production section 28 where the code patterns of thefirst code C1 and the second code C2 are different from each other. Thevariable capacitor 22, whose capacitance varies in response to thepressure applied to the first electrode 20, is connected at one terminalthereof to the ground. The variable capacitor 22 is connected at theother terminal thereof to the power production circuit 25 through aresistor 144 such that a predetermined voltage Vcc is supplied thereto.

A timing control circuit 141 carries out ON/OFF control of a switch 143in a predetermined period t1. In particular, the switch 143 is turned ONonce by the timing control circuit 141 to discharge the charge of thevariable capacitor 22 and is then turned OFF. Further, while turning theswitch 143 OFF, the timing control circuit 141 instructs the first codeproduction section 26 to produce a first code C1. When the switch 143 isOFF, the variable capacitor 22 is gradually charged through the resistor144. Thereupon, the potential between the opposite terminals of thevariable capacitor 22 gradually increases depending upon the capacitancevalue which varies in response to the pressure.

A delay setting circuit 142 carries out comparison between the potentialof the variable capacitor 22 and a predetermined potential Vth inresponse to supply of a control signal from the timing control circuit141. If the potential of the variable capacitor 22 reaches thepredetermined potential Vth, then the delay setting circuit 142instructs the second code production section 27 to produce a second codeC2. By the configuration described above, the difference between thecode production timing of the first code C1 from the first codeproduction section 26 and the code production timing of the second codeC2 from the second code production section 27, that is, the timedifference between the first code C1 and the second code C2, variesbased on the capacitance value which is varied in response to thepressure applied to the pen tip. Thus, the pressure can be detected bydetecting the time difference.

FIG. 3B shows an example of a circuit configuration of the transmissioncode production section 28 where the same pattern is used for the firstcode C1 and the second code C2. In other words, a circuit configurationwhere a single code is used is shown. In this example, the first codeproduction section 26 is used in place of the second code productionsection 27 shown in FIG. 3A, but the configuration of the other part isthe same. Where the first code C1 and the second code C2 have the samecode pattern as in the present example, the time difference between themvaries in response to the pressure, and consequently, the pressure canbe detected by detecting the time variation, also.

[Configuration of the Position Detector]

FIG. 4 shows a general configuration of the position detector 3. Theposition detector 3 includes, as principal components thereof, a sensorsection 30 for detecting a pointing position of the pointer 2, aselection circuit 40 for selecting a plurality of conductors which formthe sensor section 30, and a position detection circuit 50. It is to benoted that, in FIG. 4, a flow of processing of a reception signal isindicated by a solid line arrow mark, and a flow of a control signal, aclock signal or the like is indicated by a broken line arrow mark. It isto be noted, however, that, in FIG. 4, broken line arrow marksindicative of flows of a control signal, a clock signal and so forth ofa reception system circuit group 51 are omitted in order to simplify thedescription.

The sensor section 30 includes a first conductor group 32 including aplurality of first conductors 31 extending in an x direction(predetermined direction) in FIG. 4, a second conductor group 34including a plurality of second conductors 33 extending in a directioncrossing with the extension direction of the first conductors 31, thatis, in a y direction in FIG. 4, and the excitation coil 35 provided onan outer periphery of the conductor groups. The plurality of firstconductors 31 which form the first conductor group 32 are disposed in apredetermined spaced relationship from each other and in parallel toeach other in the y direction in FIG. 4. Meanwhile, the plurality ofsecond conductors 33 which form the second conductor group 34 aredisposed in a predetermined spaced relationship from each other and inparallel to each other in the x direction in FIG. 4.

It is to be noted that the first conductors 31 and the second conductors33 are formed, for example, from a transparent electrode film formedfrom an ITO (Indium Tin Oxide) film, a copper foil or the like. Further,the first conductor group 32 and the second conductor group 34 arelaminated with a spacer, which is made of a resin material or the likeor a glass substrate or the like (not shown) interposed therebetween.Further, the conductors of the first conductor group 32 and the secondconductor group 34 are connected to the selection circuit 40. Theexcitation coil 35 is connected to a drive circuit 61 hereinafterdescribed in the position detection circuit 50.

The number and the pitch of the first conductors 31 and the secondconductors 33 are set suitably according to the size of the sensorsection 30, required detection accuracy and so forth. Further, while, inthe present embodiment, a linear conductor is illustrated as the firstconductors 31 and the second conductors 33, the present invention is notlimited to this configuration. For example, both of the first conductors31 and the second conductors 33 may meander in directions crossing withthe extension directions. Further, one of the first conductors 31 andthe second conductors 33 may be formed as ring-shaped conductors and theother conductors may be formed as conductors which extend in radialdirections from the center of the ring-shaped conductors.

The selection circuit 40 selects a predetermined conductor from withinthe first conductor group 32 and the second conductor group 34 in apredetermined order so as to select them in order. The conductorselection control by the selection circuit 40 is controlled by a controlsignal (broken line arrow mark in FIG. 4) outputted from a controlsection 63, which cooperates with a central processing unit 62hereinafter described. It is to be noted that, in the presentembodiment, the sensor section 30 at least has a configuration forreceiving a predetermined signal transmitted from the pointer 2.Further, in the present embodiment, in order to time-divisionallyoperate the reception system circuit group 51, a configuration isprovided for detecting the position (X coordinate and Y coordinate)pointed to by the pointer 2 by selecting a predetermined conductor fromwithin each of the first conductor group 32 and the second conductorgroup 34 by means of the selection circuit 40. It is to be noted that,if a configuration which includes a plurality of reception systemcircuit groups 51 corresponding to the number of conductors which formthe sensor section 30 is adopted, then the selection circuit 40 can beomitted.

The position detection circuit 50 includes a reception system circuitgroup 51, an oscillator 60, a drive circuit 61, a central processingunit 62 (CPU), and a control section 63.

The oscillator 60 outputs an AC signal or a pulse signal of apredetermined frequency to the drive circuit 61. The drive circuit 61converts the signal inputted thereto from the oscillator 60 into acurrent and outputs the current to the excitation coil 35.

The control section 63 cooperates with the central processing unit 62 tooutput control signals (broken line arrow marks in FIG. 4) to thecomponents in the position detection circuit 50 and outputs a result ofcalculation of a position and pressure calculation section 58hereinafter described in the reception system circuit group 51 to theexternal apparatus. Further, the central processing unit 62 includes asoftware program and controls operation of the control section 63.

The reception system circuit group 51 includes, as principal componentsthereof, a reception amplifier 52, an A/D (Analog to Digital) conversioncircuit 53, a serial to parallel conversion section 54, a shift register55, a correlation matching section 56, a memory 57, and a position andpressure calculation section 58 (detection section). The receptionamplifier 52, A/D conversion circuit 53, serial to parallel conversionsection 54, shift register 55, correlation matching section 56, memory57, and position and pressure calculation section 58 are connected inthis order from the selection circuit 40 side.

The reception amplifier 52 amplifies a reception signal inputted from apredetermined conductor selected by the selection circuit 40. Then, thereception amplifier 52 outputs the amplified reception signal to the A/Dconversion circuit 53. The A/D conversion circuit 53 carries out analogto digital conversion of the amplified reception signal and outputs adigital signal obtained by the conversion to the serial to parallelconversion section 54.

The serial to parallel conversion section 54 is formed, for example,from a shift register of the serial-input parallel-output type and has anumber of stages of flip-flops corresponding to the code length of acode to be used. Operation of the serial to parallel conversion section54 is controlled by the control section 63 which cooperates with thecentral processing unit 62 including an execution program. It is to benoted that, for the flip-flops of the individual stages which form theserial to parallel conversion section 54, a flip-flop which can retaininformation of 1 bit may be used or a flip-flop which can retaininformation of multi bits (for example, 10 bits or the like) may beused.

The flip-flops of the stages which form the serial to parallelconversion section 54 successively shift a reception signal inputtedthereto to the flip-flops at the succeeding stages. Further, an outputterminal of each of the flip-flops is connected to an input terminal ofa corresponding flip-flop in the shift register 55, hereinafterdescribed which is also formed from multi-stage flip-flops. As a result,a number of output signals equal to the code length of a code to be usedare outputted in parallel to the shift register 55.

The shift register 55 is a shift register of the parallel-input andoutput type and is formed from a number of flip-flops equal to the codelength of a code to be used. It is to be noted that, for the flip-flopsof the individual stages which form the shift register 55, a flip-flopwhich can retain information of 1 bit may be used or a flip-flop whichcan retain information of multi bits (for example, 10 bits or the like)may be used.

Operation of each of the flip-flops in the shift register 55 iscontrolled by the control section 63 which cooperates with the centralprocessing unit 62. Further, each of the flip-flops which form the shiftregister 55 cyclically shift a signal inputted thereto to the flip-flopsat the succeeding stages while also outputting the signal tocorresponding integrators 56 d in the correlation matching section 56.

It is to be noted that a register which functions as a buffer fortemporarily retaining signals outputted from the serial to parallelconversion section 54 may be provided between the serial to parallelconversion section 54 and the shift register 55. In this instance, whilereception signals retained in the shift register 55 are cyclicallyshifted to calculate a correlation value, signals necessary for nextcorrelation value calculation can be temporarily retained in theregister.

The correlation matching section 56 calculates a correlation valuebetween a reception signal outputted from the shift register 55 and acode having a predetermined code pattern (the code is hereinafterreferred to as a “correlation calculation code”) and outputs acorrelation value of the reception signal.

FIG. 5 shows a general configuration of the correlation matching section56, where two codes having different code patterns from each other aretransmitted from the pointer 2. The correlation matching section 56includes two correlators (a first correlator 56 a and a secondcorrelator 56 b).

The first correlator 56 a calculates a correlation value using acorrelation calculation code corresponding to a first code C1 outputtedfrom the first code production section 26 of the pointer 2 (firstcorrelation calculation code). In this case, for example, where a PNcode which is a representative spread code is used, a correlationcalculation code having the same code pattern as that of the first codeC1 is used. Meanwhile, the second correlator 56 b calculates acorrelation value using a correlation calculation code corresponding toa second code C2 outputted from the second code production section 27 ofthe pointer 2 (second correlation calculation code).

It is to be noted that, where two codes transmitted from the pointer 2have the same code pattern, the first correlator 56 a and the secondcorrelator 56 b use the same correlation calculation code. In thisinstance, a single correlator can be used to carry out the signalprocessing. Furthermore, where two kinds of codes are used, it ispossible to use a configuration which uses one of the codes in acalculation process of a position based on an output signal from thefirst conductor 31 (Y coordinate) while using the other code in acalculation process of a position based on an output signal from thesecond conductor 33 (X coordinate) in a position calculation process fordetermining a position (X coordinate and Y coordinate) pointed to by thepointer 2.

FIG. 6 shows a general configuration of the first correlator 56 a. It isto be noted that the configuration of the second correlator 56 b issimilar to the configuration of the first correlator 56 a shown in FIG.6 except that the correlation calculation code to be used is different.Therefore, description of the configuration of the second correlator 56b is omitted.

The first correlator 56 a includes a correlation calculation codeproduction section 56 c, a number of integrators 56 d corresponding tothe code length of a correlation calculation code, and an adder 56 e. Itis to be noted that, in the present embodiment, each of the integrators56 d is connected to an output terminal of a corresponding flip-flop ofthe shift register 55. Further, in the example shown in FIG. 6, the codelength of the correlation calculation code is 11. Therefore, in theexample shown in FIG. 6, 11 integrators 56 d (integrators I₁ to I₁₁ inFIG. 6) are provided.

In the example shown in FIG. 6, an example wherein a PN code is used isillustrated, and a reception signal (PS₁ to PS₁₁) of a code length of 11outputted from the shift register 55 is inputted to the integrators I₁to I₁₁. Further, a correlation calculation code (PN₁ to PN₁₁) of a codelength of 11 outputted from the correlation calculation code productionsection 56 c is inputted to the integrators I₁ to I₁₁, respectively. Theintegrators I₁ to l₁₁ integrate the signal PS₁ to PS₁₁ outputted fromthe shift register 55 and the code PN₁ to PN₁₁ outputted from thecorrelation calculation code production section 56 c, respectively, andoutput results of the integration to the adder 56 e.

The adder 56 e adds the output signals from the integrators 56 d andoutputs the sum value as a correlation value. Thereupon, if a signalstring pattern of the reception signal PS₁ to PS₁₁ outputted from theshift register 55 and a code pattern of the code PN₁ to PN₁₁ outputtedfrom the correlation calculation code production section 56 c coincidewith each other, then signals of the same polarity are outputted fromall of the integrators 56 d and a maximum correlation value is outputtedfrom the adder 56 e. In any other case, since the polarities of signalsoutputted from the integrators 56 d are different, a low valueindicative of no correlation is outputted from the adder 56 e.

It is to be noted that, where the code length of the reception signalretained in the shift register 55 is 11 as in the present example, inthe first correlator 56 a, the reception signal PS₁ to PS₁₁ retained inthe shift register 55 are cyclically shifted by 10 cycles to verifycoincidence with the code pattern of the code PN₁ to PN₁₁ outputted fromthe correlation calculation code production section 56 c. However, thepresent invention is not limited to this configuration, and anotherconfiguration may be adopted wherein, in place of cyclically shiftingthe reception signal PS₁ to PS₁₁ and supplying the cyclically shiftedreception signal PS₁ to PS₁₁ from the shift register 55 to theintegrators 56 d, the code pattern of the code PN₁ to PN₁₁ outputtedfrom the correlation calculation code production section 56 c iscyclically shifted and then supplied to the integrators 56 d.

FIGS. 7A-7C particularly illustrate the operation of the firstcorrelator 56 described above and a calculation principle of acorrelation characteristic. It is assumed that a reception signaloutputted from the shift register 55 has a time differencecorresponding, for example, to an 8-chip length (8T) relative to thecorrelation calculation code (refer to FIGS. 7A and 7B).

In this instance, from the start of calculation of a correlation valueuntil time 8T (T: unit time for code processing) corresponding to the8-chip length, the code pattern of the reception signal outputted fromthe shift register 55 and the code pattern of the correlationcalculation code outputted from the correlation calculation codeproduction section 56 c are different from each other. Therefore, a lowvalue representative of no correlation is outputted from the firstcorrelator 56 a (refer to FIG. 7C). Then, when time 8T elapses, bothcode patterns coincide with each other. Thereupon, signals of the samepolarity are outputted from all of the integrators 56 d as describedhereinabove, and the correlation value exhibits the maximum value.Thereafter (after time 8T has elapsed), since both code patterns becomedifferent from each other, the correlation value changes back to the lowvalue. Therefore, if a correlation between the reception signal and thecorrelation calculation code is determined by the correlator, then acorrelation characteristic is obtained wherein the correlation valuebetween the two codes exhibits a peak (singular value) at a point oftime when both code patterns satisfy a predetermined time relationship,as seen in FIG. 7C.

In the correlation matching section 56, for each conductor selected forsignal detection, a correlation characteristic relative to the firstcode C1 for position detection is determined by the first correlator 56a and a correlation characteristic relative to the second code C2 forpressure detection is determined by the second correlator 56 b, based onthe calculation principle of a correlation characteristic (correlationvalue) described hereinabove. Then, the correlation characteristics areoutputted to the memory 57. It is to be noted that, where the codepatterns of the first code C1 for position detection and the second codeC2 for pressure detection are set the same as each other, it is possibleto use a single correlator to determine the correlation characteristics.

Further, the position and pressure calculation section 58 calculates apointing position (coordinates) and pressure of the pointer 2 from thecorrelation characteristics calculated based on the signals generated inthe conductors and stored in the memory 57. In particular, the positionand pressure calculation section 58 detects a peak of a correlationvalue from the correlation characteristic relative to the first code C1for position detection to carry out position detection of the pointer 2.In this case, the position detection circuit 50 identifies the pointer 2which transmits a code pattern corresponding to a code pattern of acorrelation calculation code used in the position detection circuit 50and cooperates with the conductor selection control of the selectioncircuit 40 to determine the position (X coordinate and Y coordinate)pointed to by the identified pointer 2.

Further, in the present embodiment, the pointer 2 includes aconfiguration that the time difference between the first code C1 forposition detection and the second code C2 for pressure detection variesin response to the pressure, as described hereinabove. In particular, inthe present embodiment, the production timing of the second code C2 withrespect to the production time of the first code C1 is controlled inresponse to the pressure, and the second code C2 is transmitted.Therefore, the peak position (time) of the correlation value obtainedfrom the correlation characteristic relative to the second code C2 andthe peak position (time) of the correlation value obtained from thecorrelation characteristic relative to the first code C1 are differentaccording to the pressure. In the present embodiment, the pressure isdetermined based on the time difference between the peak positions oftheir respective correlation values. It is to be noted that thecalculation principles of the position and the pressure of the pointer 2are hereinafter described more particularly.

Operation of the Position Detection Apparatus

Now, operation of the position detection apparatus 1 of the presentembodiment and the principles of position and pressure detection aredescribed with reference to FIGS. 8 to 10. FIG. 8 is a flow chartillustrating operation of the pointer 2 of the present embodiment. FIG.9 is a flow chart illustrating operation of the position detector 3.Further, FIGS. 10A-10C are views illustrating a transmission operation,a waveform of a reception signal, and a correlation characteristic uponoperation of the position detection apparatus 1 of the presentembodiment, respectively.

First, operation of the pointer 2 is described with reference to FIG. 8Aand FIG. 10. First, the pointer 2 transmits a first code C1 for positiondetection from the first code production section 26 through the firstelectrode 20 and the second electrode 21 (step S1). Then, at a point oftime at which a time period corresponding to the pressure elapses, thepointer 2 transmits a second code C2 for pressure detection from thesecond code production section 27 through the first electrode 20 and thesecond electrode 21 (step S2).

Then, the pointer 2 determines whether or not the processing time afterthe start of transmission of the first code C1 (step S1) reaches apredetermined time period t1 sufficient to have transmitted a codepattern of the second code C2 (step S3). If the processing time afterthe start of transmission of the first code C1 does not reach thepredetermined time period t1 sufficient to have transmitted the codepattern of the second code C2, that is, if the decision at step S3 isNO, then the pointer 2 waits until the predetermined time period t1lapses. On the other hand, if the processing time after the start oftransmission of the first code C1 exceeds the predetermined time periodt1, that is, if the decision at step S3 is YES, then the processingreturns to step S1.

In the pointer 2, a series of processes of transmitting a first code C1and then, after a time period corresponding to the pressure elapses,transmitting a second code C2, as described hereinabove, are executedrepetitively. A manner of this operation is illustrated in FIG. 10A. Inthis example, a first code C1 for determining a position pointed to by apointer and a second code C2, whose transmission is started at a pointof time at which a predetermined time period Td corresponding to thepressure elapses after the transmission starting time of the first codeC1, are temporally multiplexed through the first electrode 20 and thesecond electrode 21 and transmitted from the pointer 2 as illustrated inFIG. 10A.

It is to be noted that, after the transmission of the second code C2 iscompleted, the transmission of the first code C1 (step S1) is startedagain after a predetermine time period (t2) has elapsed from the startof transmission of the first code C1.

It is to be noted that it is possible to make the code pattern of thefirst code C1 and the code pattern of the second code C2 the same aseach other, as described hereinabove.

Now, operation of the position detector 3 is described with reference toFIGS. 9 and 10B and 10C. The position detector 3 carries out positionand pressure detection of the pointer 2 in the following manner. First,the selection circuit 40 selects a predetermined conductor from withinthe conductor groups of the sensor section 30 (step S11). Then, thereception system circuit group 51 detects a reception signal (step S12).Then, the reception system circuit group 51 carries out amplificationand analog to digital conversion of the reception signal. Then, thecorrelation matching section 56 is used to calculate a correlation valuebetween a correlation calculation code corresponding to the first codeC1 and the reception signal, and a correlation value between acorrelation calculation code corresponding to the second code C2 and thereception signal, to determine correlation characteristics (first andsecond correlation characteristics), respectively, and stores thecorrelation characteristics in the memory 57 (step S13).

Then, in step S14, the position detector 3 determines whether or not thepredetermined time period t2, required for the series of processes afterthe start of selection of a reception conductor until the detection ofthe pointing position and the pressure of the pointer 2, has elapsedfrom the selection process of a reception conductor (step S11). It is tobe noted that the predetermined time period t2 is set to a time periodlonger than the predetermined time period t1 of the pointer 2, describedhereinabove.

It is to be noted that, if the predetermined time period t2 has notelapsed after the selection process of a reception conductor (where thedecision at step S14 is NO), then the position detector 3 waits untilthe predetermined time period t2 lapses.

When the predetermined time period t2 lapses, that is, when the decisionat step S14 becomes YES, it is determined whether or not all receptionconductors have been selected (step S15). If the decision at step S15 isNO, then the processing returns to the reception conductor selection atstep S11. On the other hand, if the decision at step S15 is YES, thenthe position and pressure calculation section 58 in the reception systemcircuit group 51 calculates the position (coordinates) pointed to by thepointer 2 based on the first correlation characteristic stored in thememory 57, more particularly based on a peak of the correlation value.Further, pressure applied to the pointer 2, so-called pen pressure, iscalculated based on the time difference between the first correlationcharacteristic and the second correlation characteristic, moreparticularly, the time difference between the two peaks of thecorrelation values (step S16).

Here, the principles of position and pressure detection of the pointer 2at step S16 described above are described with reference to FIGS. 10Band 10C. Where the pointer 2 exists on the conductor selected at stepS11 described hereinabove, within the predetermined time period t1 forposition detection and pressure detection, a signal including the firstcode C1 and the second code C2 is transmitted from the pointer 2. In theselected reception conductor, a reception signal Sp1 corresponding tothe transmission signal is generated (refer to FIG. 10B).

The reception signal Sp1 supplied to the correlation matching section 56is inputted in parallel to the first correlator 56 a and the secondcorrelator 56 b. The first correlator 56 a uses the correlationcalculation code corresponding to the first code C1 to calculate acorrelation characteristic p1 between the correlation calculation codeand the reception signal Sp1. It is to be noted that, in this example, aPN code is used as the first code C1. Accordingly, as the firstcorrelation calculation code, a PN code which is the same as the firstcode C1 is used. From the first correlator 56 a, a correlation value isoutputted, which exhibits a maximum value (peak p1 in FIG. 10C) at apoint of time at which the code patterns of the reception signal Sp1 andthe correlation calculation code coincide with each other but exhibits alow correlation value at any other time period.

Meanwhile, the second correlator 56 b uses the correlation calculationcode corresponding to the second code C2 to calculate a correlationcharacteristic p2 between the correlation calculation code and thereception signal Sp1. Similarly as in the case of the first correlator56 a, since a PN code is used as the second code C2 in this example, aPN code which is the same as the second code C2 is used as the secondcorrelation calculation code. From the second correlator 56 b, acorrelation value is outputted, which exhibits a maximum value (peak p2in FIG. 10C) at a point of time at which the code patterns of thereception signal Sp1 and the correlation calculation code coincide witheach other but exhibits a low correlation value at any other timeperiod.

It is to be noted that, when a pointer 2 does not exist on the selectedconductor, a peak of the correlation value does not appear. Further, thetime difference between the peaks p1 and p2 of the two correlationvalues, that is, the time difference (ΔC in FIG. 10C), variescorresponding to the pressure. Accordingly, in the correlationcharacteristic illustrated in FIG. 10C, the position of the pointer 2can be detected from the peak p1 or the peak p2 of the correlationvalue. Further, by detecting the time difference ΔC between the peaks p1and p2 of the two correlation values, the pressure applied to thepointer 2 can be detected.

Then, in the present embodiment, the position and pressure calculationsection 58 determines a peak level of the correlation value of thecorrelation characteristic p1 to determine whether or not a pointer 2exists on the selected conductor. Further, the position and pressurecalculation section 58 determines the time difference (ΔC) between thepeak level of the correlation value of the correlation characteristic p1and the peak level of the correlation value of the correlationcharacteristic p2 to determine the pressure applied to the pointer 2,that is, the pen pressure.

As described above, in the present embodiment, by transmitting first andsecond codes from the pointer 2, position detection of a pointer iscarried out based on the first code, and information other than theposition information such as, for example, pressure information isdetected based on the time difference between the first code and thesecond code. It is to be noted that the first and second codes may becodes having code patterns different from each other or having the samecode pattern as each other.

When the same code pattern is used, the pointer 2 varies the signalingtiming of one code with respect to the signaling timing of the othercode in response to the pressure. Therefore, in this instance also, bycarrying out the correlation matching operation process, two peaksappear in the correlation characteristic, and not only the position ofthe pointer 2 but also the pressure can be detected. It is to be notedthat, where the code patterns of the two codes to be transmitted fromthe pointer 2 are the same as each other, since it is necessary toprovide only one correlator, the configuration of the correlationmatching section 56 is further simplified. Further, as the code, it isonly necessary for a desired correlation matching operation result to becalculated by the correlation matching operation process, and forexample, a PN code (spread code) can be applied.

[Modification 1]

While the embodiment described above is an example wherein two codes(first code C1 and second code C2) transmitted from the pointer 2 areused to determine the position and the pressure of the pointer 2, thepresent invention is not limited to this configuration. It is possibleto use two codes transmitted from a pointer to detect not only theposition of the pointer but also, for example, information regardingwhether or not the pointer is contacting the sensor section (theinformation is hereinafter referred to as “pen down” information). Inthe description of modification 1, an example is described wherein twocodes transmitted from a pointer are used to detect the position of thepointer, a state in which the pointer is positioned in the proximity of(but above) the sensor section (hovering state), and another state inwhich the pointer is in contact with the sensor section (pen downstate).

First, a first example is described with reference to FIG. 2. In thisfirst example, the configuration described hereinabove for pressuredetection is applied. In particular, whether or not a pressure higherthan a predetermined value is applied to a pointer is detected todetermine whether the pointer is in a state wherein it is positioned inthe proximity of the sensor section (hovering state) or another statewherein it is contacting the sensor section (pen down stage). Also inthis first example, it is apparent that two codes transmitted from thepointer may have code patterns different from each other or the same aseach other.

Now, a second example is described. FIG. 11 shows a generalconfiguration of a pointer of this second example. It is to be notedthat, in FIG. 11, like elements to those of the embodiment (FIG. 2)described hereinabove are denoted by like reference characters. Further,for the first code and the second code, for example, a PN code (spreadcode) is used.

The pointer 100 of this example includes a first electrode 20 having ashape of a rod, a switch 101 (first switch), an integrated circuit 102,a coil 24, a power production circuit 25, and a housing 129 whichaccommodates the components mentioned above. The configuration of thepointer 100 except the switch 101 and the integrated circuit 102 aresimilar to that of the first embodiment described hereinabove, andtherefore, the configuration of only the switch 101 and the integratedcircuit 102 is described.

The switch 101 is provided between the housing 129 and a changeoverswitch 103, hereinafter described, within the integrated circuit 102.Further, the switch 101 is engaged with the first electrode 20 andconfigured such that, when the first electrode 20 functioning as the pentip is pressed on the scannable region 3 a, then the switch 101 isplaced into an ON state.

The integrated circuit 102 includes a transmission code productionsection 28 including a first code production section 26 and a secondcode production section 27, and a changeover switch 103 (second switch).It is to be noted that the transmission code production section 28 has aconfiguration similar to that of the embodiment described hereinabove.

The changeover switch 103 is connected at an input terminal thereof tooutput terminals of the first code production section 26 and the secondcode production section 27 and at an output terminal thereof to thefirst electrode 20. The changeover switch 103 selects which one of afirst code C1 and a second code C2 should be transmitted. The changeoveroperation of the changeover switch 103 is controlled by a connectionstate (ON or OFF state) of the switch 101. In particular, when theswitch 101 is in an OFF state (where the pointer 100 is in a hoveringstate wherein it is afloat above the sensor section), the changeoverswitch 103 is connected to the second code production section 27, butwhen the switch 101 is in an ON state (where the pointer 100 is placedin a pen down state wherein it is contacting the sensor section), thechangeover switch 103 is connected to the first code production section26.

In particular, when the pointer 100 is afloat above the sensor section,the second code C2 is transmitted from the pointer 100 to the sensorsection. In this instance, the sensor section detects a peak of thecorrelation value from the reception signal corresponding to the secondcode C2, to thereby detect that the pointer 100 is in a hovering stateand the position of the pointer 100 in the hovering state. On the otherhand, when the pointer 100 contacts the sensor section, the first codeC1 is transmitted from the pointer 100 to the sensor section. In thisinstance, the sensor section detects a peak of the correlation valuefrom the reception signal corresponding to the first code C1 to carryout position detection. In this manner, by identifying the type (C1 orC2) of the code transmitted, it can be determined whether the pointer100 is in a pen down state wherein it is contacting the sensor sectionor in a hovering state. This can be carried out, for example, bydetermining from which one of outputs of the first correlator and thesecond correlator of a correlation matching section in the receptionsystem circuit group a peak of the correlation value is obtained.

It is to be noted that, also in this example, the first code productionsection 26 and the second code production section 27 are provided in theintegrated circuit 102, but the present invention is not limited to thisconfiguration. Another configuration may be used wherein, for example, aROM is provided in the integrated circuit 102 and the first code C1 andthe second code C2 are stored in the ROM such that, when transmitting aspread code, the codes are read out from the ROM and transmitted.

[Modification 2]

In the description of modification 2, examples of a configuration of apointer are provided, which can detect operational information of a sideswitch of the pointer, in addition to the position and the pressure ofthe pointer, using a plurality of codes transmitted from the pointer.

FIGS. 12A and 12B show a general configuration of the pointers of thisexample. It is to be noted that, in FIGS. 12A and 12B, like elements tothose of the embodiment described hereinabove (FIG. 2) are denoted bylike reference characters.

The pointer 110 illustrated in FIG. 12A includes a first electrode 20having a shape of a rod, a cylindrical second electrode 21, a variablecapacitor 22, an integrated circuit 111, a coil 24, a power productioncircuit 25, and a housing 129 which accommodates the componentsmentioned above. Further, the pointer 110 includes an operation switchprovided at a part of a side face of the housing 129, to be operated bya finger or the like, that is, a so-called side switch 113. Theconfiguration of any other part of the pointer 110 than the integratedcircuit 111 and the side switch 113 is similar to that of the embodimentdescribed hereinabove, and therefore, the description of only theintegrated circuit 111 and the side switch 113 is given.

The integrated circuit 111 includes a transmission code productionsection 115 including a first code production section 26 and a secondcode production section 27, a changeover switch 114, and an invertercircuit 128.

The first code production section 26 and the second code productionsection 27 have a configuration similar to that of the embodimentdescribed hereinabove and produce and output a first code C1 and asecond code C2, respectively. Further, as the codes to be produced, aspread code represented by a PN code can be applied. It is to be notedthat, the position on the sensor section pointed to by the pointer 110is detected based on the first code C1 produced by the first codeproduction section 26 as described hereinabove. Meanwhile, detection ofpressure applied to the pointer 110, that is, of so-called pen pressure,is carried out by detection of a capacitance variation of a capacitorcaused by the first electrode 20 having a shape of a rod pressing thevariable capacitor 22 in response to the pressure. In particular, asshown in FIGS. 3A and 3B, the production starting timing of the secondcode C2 which is produced by the second code production section 27 isvaried in accordance with the capacitance of the variable capacitor 22.Accordingly, the pressure can be determined by detecting the timedifference between the code production starting timings of the secondcode C2 and the first code C1 by means of the position detection circuit50.

Meanwhile, the second code C2 produced by the second code productionsection 27 is supplied to the changeover switch 114 together with anoutput inverted signal obtained from the inverter circuit 128, to whichthe second code C2 is supplied. As the changeover switch 114 iscontrolled in response to an operation of the operation switch (sideswitch) 113, the second code C2 produced by the second code productionsection 27 is supplied to the second electrode 21 through the invertercircuit 128. It is to be noted that the inverter circuit 128 and thechangeover switch 114 form a code inversion circuit 116.

According to this configuration, the interposition of the invertercircuit 128 is controlled, which carries out signal inversion of thesecond code C2 produced by the second code production section 27 inresponse to an operation of the operation switch (side switch) 113. Theposition detection circuit 50 can detect whether or not the operationswitch (side switch) 113 is operated by detecting whether or not thesecond code C2 produced by the second code production section 27 is in asignal inverted state based on the processing of the correlationmatching section 56. It is to be noted that the operation switch 113 isprovided, for example, in order to implement a function of the rightclick button or the left click button of a mouse used in a personalcomputer.

In the configuration shown in FIG. 12A, the inverter circuit 128 isprovided in the pointer 110, and a signal outputted from the invertercircuit 128 in response to an operation of the operation switch (sideswitch) 113 is supplied to the second electrode to detect presence orabsence of an operation (activation) of the operation switch (sideswitch) 113. In contrast, in the configuration of a pointer 117 shown inFIG. 12B, the second electrode 21 is formed from a first electrode piece21 a and a second electrode piece 21 b. Further, the pointer 117includes a third code production section 29 in addition to the firstcode production section 26 and the second code production section 27. Itis to be noted that, if a code pattern of a third code C3 produced bythe third code production section 29 is made different from codepatterns of the first code C1 and the second code C2 produced by thefirst code production section 26 and the second code production section27, respectively, then the correlation matching section 56 which formsthe position detection circuit 50 can differentiate the codes from oneanother.

The third code C3 produced by the third code production section 29 issupplied to the second electrode piece 21 b through a switch 112, whichis switched ON in response to an operation of the operation switch (sideswitch) 113. By detecting the third code C3 transmitted from the secondelectrode piece 21 b by means of the position detection circuit 50, itcan be detected whether or not the operation switch (side switch) 113 isoperated. It is to be noted that the second code C2 produced by thesecond code production section 27 is supplied to the first electrodepiece 21 a and used for pressure detection. While this example has theconfiguration wherein the second electrode 21 is divided into twoelements including the first electrode piece 21 a and the secondelectrode piece 21 b, the present invention is not limited to thisconfiguration, and the second electrode 21 can be divided furtherfinely. The second electrode 21 may be configured such that it isdivided into a plurality of electrode pieces disposed substantiallycylindrically such that the second code C2 is supplied to theodd-numbered ones of the electrode pieces while the third code C3 issupplied to the even-numbered ones of the electrode pieces. In thisinstance, a stabile electric coupling characteristic can be assuredirrespective of the positional relationship between the sensor sectionand a peripheral face of the pointer.

It is to be noted that this example may also be configured such that,for example, a ROM is provided in the integrated circuit 111 and thefirst code C1, second code C2 and third code C3 are stored in advance inthe ROM such that, when transmitting codes, the codes are read out fromthe ROM. Further, as described hereinabove with reference to FIGS. 3Aand 3B, the codes including the first code C1, second code C2 and thirdcode C3 may have code patterns different from one another or the samecode pattern. However, where the codes have the same code pattern, apredetermined time difference is provided among the codes. Furthermore,while this example has the configuration that the codes are supplied tocorresponding ones of the electrodes, it is also possible to supply thecodes to the same electrode, for example, by using so-called resistanceaddition wherein the codes are supplied through resistors or the like.

[Modification 3]

While, in the description of the embodiment and the modifications 1 and2 described above, codes themselves from the pointer 2 are transmitteddirectly to the position detector 3, the present invention is notlimited to this configuration. Predetermined modulation may be appliedto spread codes, and the modulated codes (transmission codes) may betransmitted from the pointer 2 to the position detector 3. In thedescription of modification 3, a spread code is used as the first andsecond codes and is PSK (Phase Shift Keying) modulated.

FIGS. 13A and 13B show waveforms of a spread code before and after PSKmodulation. FIG. 13A shows a waveform of a spread code before PSKmodulation and FIG. 13B shows a waveform of the spread code after PSKmodulation.

In this example, a spread code is PSK modulated with a signal having aclock period that is ½ the code period of the spread code beforemodulation. It is to be noted that the ratio between the clock periodused for modulation and the code period can be suitably adjusteddepending on each application. In the PSK modulation of this example,the phase is reversed at a timing of transition of the level of thespread code before modulation (FIG. 13A) from High to Low or from Low toHigh, to produce a modulated signal (FIG. 13B).

FIG. 14 shows a general configuration of a pointer configured to carryout the PSK modulation described above. It is to be noted that, in FIG.14, like elements to those of the embodiment described hereinabove (FIG.2) are denoted by like reference characters. The pointer 120 includes afirst electrode 20, a second electrode 21, a variable capacitor 22, anintegrated circuit 121, a coil 24, a power production circuit 25, and ahousing 129 which accommodates the components mentioned above. It is tobe noted that the configuration of the pointer 120 other than theintegrated circuit 121 is similar to that of the embodiment describedhereinabove, and therefore, description is given here only of theintegrated circuit 121.

The integrated circuit 121 includes a transmission code productionsection 122, which in turn includes a first code production section 26,a second code production section 27, and two PSK modulators 123 and 124.The PSK modulator 123 is connected to the output side of the first codeproduction section 26 while the other PSK modulator 124 is connected tothe output side of the second code production section 27. The first codeproduction section 26 and the second code production section 27 have aconfiguration similar to that of the embodiment described hereinabove,and both of the PSK modulators 123 and 124 can be configured from a PSKmodulator which is conventionally used in the communication technologyfield.

It is to be noted that, while, in this example, the first code C1 andthe second code C2 are produced in the transmission code productionsection 122 of the integrated circuit 121 and are PSK modulated, thepresent invention is not limited to this configuration. It is possibleto use another configuration wherein, for example, a ROM is provided inthe integrated circuit 121 and the first code C1 and the second code C2,which are PSK modulated in advance, are stored in the ROM such that,when transmitting spread codes, predetermined modulated spread codes areread out from the ROM and transmitted. It is to be noted that, in thisinstance, a corresponding relationship between capacitance variationamounts of the variable capacitor 22 and variation amounts of the phaseof the PSK modulated second code C2 is stored in advance as a table inthe ROM.

Further, since, in this example, a signal supplied to a conductor groupis PSK modulated, upon detection of a reception signal, a circuit fordemodulating the PSK modulated signal is required. FIG. 15 shows aconfiguration of the reception system circuit group in the positiondetector in this example. It is to be noted that, in FIG. 15, likeelements to those of the embodiment (FIG. 4) described hereinabove aredenoted by like reference characters.

The reception system circuit group 125 includes, as principal componentsthereof, a reception amplifier 52, an A/D conversion circuit 53, a PSKdemodulator 126, a serial to parallel conversion section 54, a shiftregister 55, a correlation matching section 56, a memory 57, and aposition and pressure calculation section 58. The reception amplifier52, A/D conversion circuit 53, PSK demodulator 126, serial to parallelconversion section 54, shift register 55, correlation matching section56, memory 57 and position and pressure calculation section 58 areconnected in this order from the input side of a reception signal. Inparticular, in the reception system circuit group 125 of this example,the PSK demodulator 126 is provided between the A/D conversion circuit53 and the serial to parallel conversion section 54. Except for this,the reception system circuit group 125 has a configuration similar tothat of the embodiment described hereinabove. It is to be noted that thePSK demodulator 126 can be formed from a PSK demodulator which isconventionally used in the communication technology field.

If a spread code to be transmitted is PSK modulated as in this example,then since a clock signal of a period shorter than the code period ofthe spread code is used, the frequency of signal transitions upon riseand fall of spread codes detected by the reception system circuit group125 can be increased, and errors in position and pressure detection canbe reduced. Further, since a spread code is PSK modulated, the frequencyrange of the transmission signal can be increased and the noisetolerance can be improved.

[Modification 4]

In modification 4, a spread code is used as the first and second codesand is FSK (Frequency Shift Keying) modulated. Waveforms of a spreadcode before and after FSK modulation are shown in FIGS. 16A and 16B,respectively. FIG. 16A shows a waveform of the spread code before FSKmodulation and FIG. 16B shows a waveform of the spread code after FSKmodulation.

In the present example described below, a spread code is FSK modulatedusing signals having clock periods equal to ½ and ¼, respectively, thecode period of the spread code before modulation. In the FSK modulationof the present example, a High level state of a spread code beforemodulation (FIG. 16A) is associated with a signal having four times thefrequency of that of the spread code before modulation, while a Lowlevel state is associated with a signal having twice the frequency ofthe spread code before modulation, to thereby obtain a modulated signal(FIG. 16B). It is to be noted that the ratio between the clock period(s)used for modulation and the code period can be suitably adjusteddepending on each application.

FIG. 17 shows a general configuration of a pointer configured to carryout the FSK modulation described above. It is to be noted that, in FIG.17, like elements to those of the embodiment described hereinabove (FIG.2) are denoted by like reference characters. The pointer 130 includes afirst electrode 20, a second electrode 21, a variable capacitor 22, anintegrated circuit 131, a coil 24, a power production circuit 25, and ahousing 129 which accommodates the components mentioned above. It is tobe noted that the configuration of the pointer 130 other than theintegrated circuit 131 is similar to that of the embodiment describedhereinabove, and therefore, description is given here only of theintegrated circuit 131.

The integrated circuit 131 includes a transmission code productionsection 132, which in turn includes a first code production section 26,a second code production section 27, and two FSK modulators 133 and 134.The FSK modulator 133 is connected to the output side of the first codeproduction section 26 while the other FSK modulator 134 is connected tothe output side of the second code production section 27. The first codeproduction section 26 and the second code production section 27 have aconfiguration similar to that of the embodiment described hereinabove,and both of the FSK modulators 133 and 134 can be configured from an FSKmodulator which is conventionally used in the communication technologyfield.

It is to be noted that, while, in this example, the first code C1 andthe second code C2 are produced in the transmission code productionsection 132 of the integrated circuit 131 and are FSK modulated, thepresent invention is not limited to this configuration. It is possibleto use another configuration wherein, for example, a ROM is provided inthe integrated circuit 131 and the first code C1 and the second code C2,which are FSK modulated, are stored in the ROM such that, whentransmitting spread codes, predetermined modulated spread codes are readout from the ROM and transmitted. It is to be noted that, in thisinstance, a corresponding relationship between capacitance variationamounts of the variable capacitor 22 and variation amounts of the phaseof the FSK modulated second code C2 is stored in advance as a table inthe ROM.

Further, since, in this example, a signal supplied to a conductor groupis FSK modulated, upon detection of a reception signal, a circuit fordemodulating the FSK modulated signal is required. FIG. 18 shows aconfiguration of the reception system circuit group in the positiondetector in this example. It is to be noted that, in FIG. 18, likeelements to those of the embodiment (FIG. 4) described hereinabove aredenoted by like reference characters.

The reception system circuit group 135 includes, as principal componentsthereof, a reception amplifier 52, an A/D conversion circuit 53, an FSKdemodulator 136, a serial to parallel conversion section 54, a shiftregister 55, a correlation matching section 56, a memory 57, and aposition and pressure calculation section 58. The reception amplifier52, A/D conversion circuit 53, FSK demodulator 136, serial to parallelconversion section 54, shift register 55, correlation matching section56, memory 57 and position and pressure calculation section 58 areconnected in this order from the input side of a reception signal. Inparticular, in the reception system circuit group 135 of this example,the FSK demodulator 136 is provided between the A/D conversion circuit53 and the serial to parallel conversion section 54. Except for this,the reception system circuit group 135 has a configuration similar tothat of the embodiment described hereinabove. It is to be noted that theFSK demodulator 136 can be formed from an FSK demodulator which isconventionally used in the communication technology field.

If a spread code to be transmitted is FSK modulated as in this example,then since a clock signal of a period shorter than the code period ofthe spread code is used, the frequency of signal transitions upon riseand fall of spread codes detected by the reception system circuit group135 can be increased, and errors in position and pressure detection canbe reduced. Further, since a spread code is FSK modulated, the frequencyrange of the transmission signal can be increased and the noisetolerance can be improved.

[Modification 5]

In the modification 2 described with reference to FIGS. 12A and 12B, aconfiguration is described for assuring a stable electric couplingcharacteristic between the sensor section and the pointer, irrespectiveof the positional relationship between the sensor section and aperipheral face of the pointer. In modification 5, a configuration isdescribed for detecting an operational state of a pointer with referenceto FIG. 19. More particularly, a configuration is described fordetecting the following three operational states.

(1) Detection of a rotational angle r around the pen tip of a pointer146 as a reference axis.

(2) Detection of the inclination θ of the pointer 146, with its pen tipas a reference point, relative to a plane of the scannable region 3 a(the plane formed by the sensor section 30 coupled to the positiondetection circuit 50).

(3) Detection of the rotational angle φ of the pointer 146 when thepointer 146 is projected to the plane of the scannable region 3 a (or aplane parallel to that plane), where the pointer 146 is rotated with itspen tip as a reference point while maintaining the inclination θ, thatis, where the pointer 146 is rotated in such a manner as to draw a conewith its pen tip as a reference point while maintaining the inclinationθ.

It is to be noted that those elements which have already been describedhereinabove are denoted by like reference characters and description ofthem is omitted. Further, as hereinafter described, information (r, θ,φ) is set with reference to a predetermined electrode piece disposed inthe housing of the pointer 146.

It is assumed that, in FIG. 19, the pointer 146 itself is positioned ata predetermined rotational angle r around the center of rotationprovided by the pen tip (axis), which forms the first electrode 20.Further, it is assumed that the pointer 146 points to a position withthe inclination θ with respect to the plane of the scannable region 3 aof the position detector 3, with its pen tip that forms the firstelectrode 20 as a reference point. Furthermore, it is assumed that,where the pointer 146 is rotated so as to draw a circle on the plane ofthe scannable region 3 a with its pen tip as a reference point whilemaintaining the inclination θ, that is, where the pointer 146 is rotatedsuch that a cone having the apex at the pen tip is formed by a locus ofmovement of the pointer 146, the pointer 146, when projected to theplane of the scannable region 3 a (in FIG. 19, a plan parallel to theplane mentioned above), has a rotational angle φ.

Further, a plurality of reception conductors X1, X2, X3, Y1, Y2 and Y3shown in FIG. 19 are schematically represented to detect the information(r, θ, φ) of the pointer 146. It is to be noted that the receptionconductors X1, X2 and X3 correspond to the second conductors 33 whichform the second conductor group 34. Meanwhile, the plurality ofreception conductors Y1, Y2 and Y3 correspond to the first conductors 31which form the first conductor group 32. In order to facilitateunderstanding, it is assumed that the pen tip of the pointer 146 isdisposed at a crossing point of the reception conductors X2 and Y2 andthe pointer 146 is inclined by the angle θ toward the receptionconductor Y3 side along a direction perpendicular to the receptionconductors Y1, Y2 and Y3, that is, along a direction in which thereception conductors X1, X2 and X3 extend.

In the embodiment shown in FIG. 20, a transmission signal productionsection 73 of an integrated circuit 72 accommodated in the pointer 146includes a first code production section 26, a second code productionsection 27, a third code production section 29, a fourth code productionsection 65, and a fifth code production section 66, which produce andoutput a first code C1, a second code C2, a third code C3, a fourth codeC4 and a fifth code C5, respectively. It is to be noted that aconfiguration that the codes have code patterns different from eachother such that they can be identified from each other may be adopted oranother configuration that the codes are produced with a predeterminedtime difference given therebetween so that they can be identified on thetime axis may be adopted. It is to be noted that, where the codes areproduced with a predetermined time difference given therebetween, thecodes may be configured such that they have a plurality of code patternsor may be configured such that they have the same code pattern. Inshort, any configuration may be used as long as the codes can beidentified from each other and detected on the side of the positiondetector 3. In this embodiment, it is assumed that the first code C1,second code C2, third code C3, fourth code C4 and fifth code C5 havecode patterns different from one another.

A second electrode 211 is composed of a plurality of electrode pieces(211 a, 211 b, 211 c and 211 d) electrically divided from one anotherand disposed along a circumferential face of the inner side of thehousing 129 in the proximity of the pen tip of the pointer 146. A signalof the third code C3 is supplied to the electrode piece 211 a; a signalof the second code C2 is supplied to the electrode piece 211 b; thefourth code C4 is supplied to the electrode piece 211 c; and the fifthcode C5 is supplied to the electrode piece 211 d. Further, the signal ofthe first code C1 is supplied to the first electrode 20. When thevariable capacitor 22 is pressed by pressure applied to the firstelectrode 20, the capacitance of the variable capacitor 22 varies, andas a result, the pressure can be detected as described hereinabove. Inthe present embodiment, the second electrode 211 is composed of aplurality of electrode pieces, and a plurality of codes having differentcode patterns from one another are respectively supplied to theplurality of electrode pieces. It is to be noted that it is possible tosupply a plurality of codes having a time difference from each other andhaving the same code pattern to the plurality of electrode pieces.

Now, a detection principle of the information (r, θ, φ) is described.Further, in detecting each information, the arrangement position of theelectrode piece 211 a in the housing of the pointer 146 and a codesupplied to the electrode piece 211 a are described, as references tothe information (r, θ, φ).

First, detection of the rotational angle r (rotational position r) isdescribed. In order to facilitate understanding, it is assumed that thepointer 146 points to a crossing point between the reception conductorX2 and the reception conductor Y2 and the position is pointed to in thevertical direction with respect to the plane of the scannable region 3a. In other words, it is assumed that the inclination θ is 90 degrees.If, in this state, the pointer 146 is rotated along the circumferentialface thereof around the pen tip, then the distance, for example, betweenthe reception conductor Y2 and the electrode pieces 211 a, 211 b, 211 cand 211 d which form the second electrode 211 varies in response to therotation of the pointer 146. Consequently, the detection signal levelwhen each code is received through each electrode piece on the receptionconductor Y2 varies. Accordingly, by detecting the variation of thesignal level of each code, the rotational position r of the pointer 146can be detected, with reference to the detection signal from theelectrode piece 211 a.

It is to be noted that, as a reception conductor used when therotational angle r is detected, it is also possible to use the receptionconductor X2 in place of the reception conductor Y2. Further, if thedetection signal level of a plurality of codes detected by a pluralityof reception conductors (for example, Y1, Y2 and Y3 or X1, X2 and X3) orall reception conductors (for example, X1, X2, X3, Y1, Y2 and Y3) isused, then the rotational position r can be determined moreparticularly.

Now, detection of the inclination θ of the pointer 146 with respect tothe plane of the scannable region 3 a with its pen tip as a referencepoint is described. It is assumed that the pointer 146 is inclined so asto exhibit an inclination θ along the extending direction of thereception conductor X2 in a state wherein the rotational position r ismaintained as seen in FIG. 19. In this state, the detection signal levelfrom the reception conductor Y3 is higher than the detection signallevel from the reception conductor Y1. Accordingly, the inclination θ ofthe pointer 146 can be determined by comparing the detection signallevels from a plurality of reception conductors disposed in theproximity of the position pointed to by the pointer 146. It can bereadily recognized that, where the pointer 146 is inclined so as toexhibit the inclination θ along the extending direction of the receptionconductor Y2, the inclination of the pointer 146 can be detected basedon a similar principle.

Further, the rotational angle φ of the pointer 146 obtained byprojecting the position of the pointer 146, which is rotated whilemaintaining the inclination θ with its pen tip as a reference point, tothe plane of the scannable region 3 a can be detected by developing thedetection principle of the inclination θ described above. In particular,the rotational angle φ of the pointer 146 can be detected by comparingthe detection signal levels from a plurality of reception conductors,for example, the reception conductors Y1, Y2 and Y3 and/or the receptionconductors X1, X2 and X3.

According to such a configuration as shown in FIG. 20, since thedistances between the electrode pieces disposed in the housing of thepointer 146 and a predetermined reception conductor are different fromeach other, as a result, electric coupling relationships between theindividual electrode pieces and the reception conductor differ from oneanother. Accordingly, by comparing the signal levels when the codes (C2,C3, C4 and C5) are detected with respect to a predetermined receptionconductor with each other, the information (r, θ, φ) representative of astate of the pointer 146 can be detected.

It is to be noted that, while, in the description of the presentembodiment, the detection principle of the information (r, θ, φ) isdescribed using the second electrode 211 composed of four electrodepieces, the number of electrode pieces is not limited to this specificnumber. Further, as the first code C1 used for detection of the pointingposition of the pointer 146, a code having the same code pattern as thatof the other codes can be used, as described hereinabove. While, in thisembodiment, the plurality of electrode pieces (211 a, 211 b, 211 c and211 d) have a structure such that they are disposed in a circularpattern inside the housing 129 of the pointer 146, it is otherwisepossible to use a structure such that they are disposed on an outerperipheral portion of the pointer 146, for example, near the pen tip.

[Modification 6]

In the position detector 3 of the embodiment shown in FIG. 4, apredetermined conductor is selected from within the first conductorgroup 32 and the second conductor group 34, but the present invention isnot limited to this configuration. The selection circuit may be composedof two selection circuits, one of which is used as a selection circuitfor selecting a predetermined conductor from within the first conductorgroup 32 while the other is used as a selection circuit for selecting apredetermined conductor from within the second conductor group 34. Alsoin this example, a spread code may be used as the first and secondcodes.

FIG. 21 shows a general configuration of a position detector ofmodification 6. It is to be noted that, in FIG. 21, like elements tothose of the embodiment (FIG. 4) described hereinabove are denoted bylike reference characters. Further, in FIG. 21, only components around aselection circuit 201 are shown to simplify the description.

The selection circuit 201 of the position detector 200 of this exampleis composed of a first selection circuit 202 for selecting apredetermined one of the first conductors 31 in a predetermined orderfrom within the first conductor group 32, and a second selection circuit203 for selecting a predetermined one of the second conductors 33 in apredetermined order from within the second conductor group 34. Further,the first selection circuit 202 and the second selection circuit 203 areconnected to the reception system circuit group 51. It is to be notedthat the configuration of the position detector 200 of the presentexample other than the selection circuit 201 is similar to that of theembodiment described hereinabove.

In the position detector 200 of the present example, operation of thefirst selection circuit 202 for selecting a predetermined one of thefirst conductors 31 from within the first conductor group 32 andoperation of the second selection circuit 203 for selecting apredetermined one of the second conductors 33 from within the secondconductor group 34 are carried out at the same time. Therefore, in thisexample, an output signal of the first selection circuit 202 and anoutput signal of the second selection circuit 203 are inputted to thereception system circuit group 51. In the present example, correlationcalculation codes respectively corresponding to the two spread codes C1and C2 are used to calculate correlation values to carry out positiondetection and pressure detection of the pointer.

Further, in the configuration of the position detector 200 of themodification 6, the reception system circuit group for processing anoutput signal of the first selection circuit 202 may be providedseparately from the reception system circuit group for processing anoutput signal of the second selection circuit 203. In this instance,both of the position detection and the pressure detection of the pointermay be carried out by both of the reception system circuit groups, orthe position detection and the pressure detection of the pointer may becarried out by one of the reception system circuit groups while only theposition detection of the pointer is carried out by the other receptionsystem circuit group. In the former case, high speed detection can beachieved. On the other hand, where the latter is applied, theconfiguration becomes simpler. It is also possible to select an outputsignal of the first selection circuit 202 and an output signal of thesecond selection circuit 203 by means of a changeover (switching)circuit and supply the selected output signals time-divisionally to acommon reception system circuit group to carry out the positiondetection and the pressure detection of the pointer.

[Modification 7]

While, in the description of the embodiment and the modifications 1 to 6described above, the position detection apparatus is a tablet, thepresent invention is not limited to this configuration. The positiondetection apparatus may have not only a function of a tablet but also afunction of a touch panel wherein a user touches a screen of a positiondetector with a finger to carry out a predetermined operation. In themodification 7, the position detection apparatus having both functionsof the tablet and the touch panel is described. In this example, aspread code is used as the first and second codes.

FIG. 22 shows a general configuration of a position detector of theposition detection apparatus of the present example. The positiondetection apparatus of the present example uses, as the pointer thereof,one of those described in connection with the embodiment and themodifications 1 to 5. Therefore, description is given here only of theconfiguration of the position detector. It is to be noted that, in FIG.22, like elements to those of the embodiment shown in FIG. 4 are denotedby like reference characters. Further, in FIG. 22, a flow of processesfor a reception signal is indicated by solid line arrow marks, and flowsof a control signal, a clock signal and so forth are indicated by brokenline arrow marks. However, in FIG. 22, broken line arrow marksindicating flows of a control signal, a clock signal and so forth of thereception system circuit group 51 are omitted to simplify thedescription.

The position detector 210 of the present example includes, as principalcomponents thereof, a sensor section 30 for detecting pointed positionsof a plurality of different types of pointers, such as a pointer 147having a shape of a pen, a plurality of fingers 148 a and 148 b and soforth as pointers, a selection circuit 220 for selecting and changing(switching) over a plurality of conductors which form the sensor section30, and a position detection circuit 230. It is to be noted that, sincethe sensor section 30 has a configuration similar to that of theembodiment shown in FIG. 4, description of the configuration of thesensor section 30 is omitted.

The selection circuit 220 is composed of a first selection circuit 221and a second selection circuit 222. The first selection circuit 221 isconnected to a first conductor group 32 composed of a plurality of firstconductors 31 disposed in parallel in a y direction in FIG. 22 andselects a predetermined one of the first conductors 31 in apredetermined order from within the first conductor group 32. Meanwhile,the second selection circuit 222 is connected to a second conductorgroup 34 composed of second conductors 33 disposed in parallel in an xdirection in FIG. 22 and selects a predetermined one of the secondconductors 33 in a predetermined order from within the second conductorgroup 34. It is to be noted that the changeover (switching) control ofthe first selection circuit 221 and the second selection circuit 222 iscontrolled by a control signal outputted from the control section 63which cooperates with the central processing unit 62.

The position detection circuit 230 includes a reception system circuitgroup 51, an oscillator 60, a drive circuit 61, a central processingunit 62, a control section 63, a spread code production section 231(code supplying section), a first changeover (switch) section 232, and asecond changeover (switch) section 233. The position detection circuit230 of the present example is configured such that it includes, inaddition to the components of the position detection circuit 50 of theembodiment (FIG. 4) described hereinabove, the spread code productionsection 231, first changeover section 232 and second changeover section233. The configuration of the other part of the position detectioncircuit 230 than the spread code production section 231, firstchangeover section 232 and second changeover section 233 is similar tothat of the embodiment described hereinabove.

Where the position detector 210 is to operate as a touch panel whichaccepts an operation by a finger, the spread code production section 231supplies a spread code to a predetermined one of the first conductors 31of the first conductor group 32. It is to be noted that the spread codeproduction section 231 preferably produces a signal having a thirdspread code C3 different from a signal of the first code C1 or a signalof the second code C2 transmitted from the pointer 147 having a shape ofa pen. However, the present invention is not limited to thisconfiguration, and it is only necessary for the spread code productionsection 231 to produce a predetermined code, which enables recognitionof multiple pen operations simultaneously, that is, recognition of thetype of a pointer such as a finger or a pen. When the position detector210 operates as a touch panel, at a position at which a finger of a usercontacts the position detector 210, since a current is shunted to theground, for example, through the finger, or a movement of the currentbetween conductors crossing with each other occurs, the level of areception signal obtained through the crossing point of the conductorsat the touched position varies. Therefore, by detecting this levelvariation by means of the reception system circuit group 51, the touchedposition can be detected two-dimensionally.

The first changeover section 232 carries out changeover between a flowof signals when the position detector 210 is to operate as a tablet foraccepting a pen operation, and a flow of signals when the positiondetector 210 is to operate as a touch panel which accepts an operationof a finger. In particular, when the position detector 210 is to operateas a tablet, since the first conductor group 32 acts as receptionconductors, an output terminal of the first selection circuit 221 isconnected to an input terminal of the second changeover section 233through a switch SW2 of the first changeover section 232. At this time,a switch SW1 of the first changeover section 232 places the spread codeproduction section 231 and the first selection circuit 221 into amutually disconnected state. On the other hand, when the positiondetector 210 is to operate as a touch panel, since the first conductorgroup 32 acts as a transmission medium, the output terminal of thespread code production section 231 is connected to the first selectioncircuit 221 through the switch SW1 of the first changeover section 232.At this time, the switch SW2 of the first changeover section 232 placesthe first selection circuit 221 and the second changeover section 233into a mutually disconnected state. It is to be noted that thechangeover operation of the first changeover section 232 is controlledby a control signal (broken line arrow mark in FIG. 22) outputted fromthe control section 63 which cooperates with the central processing unit62.

When the position detector 210 is to operate as a touch panel foraccepting an operation of a finger, the second changeover section 233connects the second selection circuit 222 and the reception amplifier 52to each other in an interlocking relationship with the connectionbetween the spread code production section 231 and the first selectioncircuit 221 through the first changeover section 232 under the controlof the control section 63 which cooperates with the central processingunit 62. Where the first changeover section 232 and the secondchangeover section 233 are controlled in this manner, a transmissionsignal produced by the spread code production section 231 issuccessively supplied to the first conductors 31 which form the firstconductor group 32 through the first selection circuit 221 while thesecond conductors 33 which form the second conductor group 34 aresuccessively selected by the second selection circuit 222 and connectedto the reception amplifier 52. By this configuration, an operation by auser can be detected two-dimensionally.

On the other hand, when the position detector 210 is to operate as atablet for accepting an operation of a pen, the second changeoversection 233 connects the first selection circuit 221 connected throughthe first changeover section 232 and the second selection circuit 222alternately to the reception amplifier 52, under the control of thecontrol section 63 which cooperates with the central processing unit 62.Since the first changeover section 232 and the second changeover section233 are controlled in this manner, the pointed position by an operationof a pen can be detected two-dimensionally.

Next, an example of operation of a function as a touch panel and afunction as a tablet of the position detector 210 of the present exampleis described briefly. In an example illustrated in FIG. 23, operation asa touch panel and operation as a tablet are switched after everypredetermined interval of time. In particular, the first changeoversection 232 and the second changeover section 233 are changed over in aninterlocked relationship with each other after every predeterminedperiod of time under the control of the control section 63, whichcooperates with the central processing unit 62, to detect presence ofpointers such as a finger and a pen or positions pointed to by thepointers. In the present example, a position detection operation (tabletfunction) of the pointer 147 having a shape of a pen and a detectionoperation (touch panel function) of the touched positions by the fingers148 a and 148 b are repeated alternately after every predeterminedperiod of time (in the example of FIG. 23, for example, 10 ms).

It is to be noted that the operation of the position detector 210 of thepresent example is not limited to the time divisional operationillustrated in the example of FIG. 23. For example, it is also possibleto detect presence of a plurality of kinds of pointers represented by afinger and a pen on the sensor section 30 at the same time. In thisinstance, the position detector 210 operates in the following manner. Itis to be noted that, in the following example of an operation, atransmission signal which includes a first spread code and a secondspread code, which is different from the first spread code, istransmitted from a pen, and a transmission signal which includes a thirdspread code different from both the first and second spread codesallocated to the pen is produced by and outputted from the spread codeproduction section 231 shown in FIG. 22.

First, the spread code production section 231 produces a transmissionsignal including the third spread code and repetitively supplies thetransmission signal in a predetermined order to a plurality of firstconductors 31, which form the first conductor group 32, through theswitch SW1 of the first changeover section 232 and the first selectioncircuit 221. Thereupon, to the reception amplifier 52 which composes thereception system circuit group 51, the selected conductor is connectedthrough the second selection circuit 222 and the second changeoversection 233. It is to be noted that the second selection circuit 222selects a predetermined conductor from among the plurality of secondconductors 33, which form the second conductor group 3,4 by a selectionoperation in accordance with a predetermined order.

Then, the A/D conversion circuit 53 converts an analog signal outputtedfrom the reception amplifier 52 into a digital signal whose one word isformed from a predetermined number of bits. Then, the serial to parallelconversion section 54 and the shift register 55 carry out serial toparallel conversion of the digital signal into a word having a wordlength corresponding to the code length of a spread code (C1, C2 andC3), and supplies the signal obtained by the conversion to thecorrelation matching section 56.

Then, the correlation matching section 56 carries out a correlationmatching operation between the digital signal supplied thereto andindividual correlation calculation codes. By this configuration,presence or absence of the first, second and third spread codes (C1, C2and C3) is detected and also their signal levels are detected.

In particular, the operation described above is the same operation fordetecting the detection operation of a touched position (touch panelfunction). Accordingly, the detection operation of the finger positionin this operation state is such as described hereinabove. In thisoperation state, if the pen is operated, then by detecting a spread codeof at least one of the first code C1 and the second code C2 transmittedfrom the pen by means of the correlation matching section 56, presenceof the pen or the pointing position of the pen can be recognized. Then,by switching to the function of the position detector 210 as a tabletbased on the recognition of the presence or absence of a pen operation,the pen position can be detected two-dimensionally.

On the other hand, if two kinds of pointers including a finger and a penare detected at the same time by the position detection circuit 230,then by switching the function of the position detector 210time-divisionally between the touch panel function and the tabletfunction as illustrated in FIG. 23, it is possible to create a statewherein operations of a finger and a pen appear to be detected at thesame time. It is also possible to switch the function setting such that,where a pen and a finger are detected at the same time, the positiondetector enters the mode for detecting one of the pen and the finger(touch panel function or tablet function).

Further, in the present example, when the position detector 210 is tooperate as a touch panel, a plurality of spread codes having phasesdifferent from each other may be supplied to corresponding ones of theplurality of first conductors 31 at the same time such that theplurality of spread codes are transmitted by phase multiplextransmission. For example, where the number of first conductors 31 is n,n spread codes having different phases from one another are producedfrom a spread code of one code pattern by the spread code productionsection 231 and are supplied in a corresponding relationship to thefirst conductors 31. Or, spread codes of n code patterns different fromone another may be produced and supplied in a corresponding relationshipto the n first conductors 31.

In this instance, the reception system circuit group 51 may adopt aconfiguration which includes correlation calculation codes correspondingto the spread codes produced by the spread code production section 231,and correlation matching operations with the individual received spreadcodes are carried out simultaneously. It is to be noted that, in thisconfiguration, at least one of the first selection circuit 221 and thesecond selection circuit 222 which form the selection circuit 220 is notnecessarily required.

Further, the position detector 210 of the present example includes aconfiguration for carrying out time-divisional switching between a touchpanel function for detecting a finger as a pointer and a pen tabletfunction for detecting a pen as a different type of pointer. However,regardless of which function is performed by the position detector 210,the second conductors 33 which form the second conductor group 34 arealways used for signal reception. Accordingly, as described hereinabove,where the reception system circuit group 51 includes a circuitconfiguration which can simultaneously detect a transmission signalsupplied from the spread code production section 231 used to detect afinger as a pointer, and a transmission signal supplied from a pen as apointer of a different type, when the finger position in the x directionis determined, the pen position in the x direction can also bedetermined simultaneously. Therefore, as a next process for determiningthe pen position, since the pen position in the x direction is acquiredalready, it is necessary to determine only the pen position in the ydirection. Accordingly, since the position detector 210 of the presentexample has such a circuit configuration as described above,simultaneous detection of a pen and a finger by the sensor section 30can be carried out at a high speed.

Furthermore, regarding detection of the presence or absence of anoperation of the side switch 113 shown in FIG. 12 (modification 2), byproviding a configuration for supplying an operational signal from theside switch 113 to the delay setting circuit 142 of FIG. 3 and switchingthe potential Vth, it can be detected that the side switch 113 isoperated. For example, the potential Vth which is set by the delaysetting circuit 142 in response to the fact that the side switch 113 isoperated is switched, for example, to a high potential. If the potentialVth is set to the high potential, then even if the pressing force by thepointer is the same, a signal outputted from the delay setting circuit12 is outputted after it is further delayed by a predetermined period oftime. By this configuration, the production timing of a signal to beoutputted from the second code production section with respect to asignal outputted from the first code production section is controlled inaccordance with the operation of the side switch 113, and as a result,the presence or absence of an operation of the side switch 113 can bedetected.

Further, while the pointer 2 shown in FIG. 2, the pointers 110 and 117shown in FIGS. 12A and 12B, the pointer 120 shown in FIG. 14, thepointer 130 shown in FIG. 17 and so forth have a configuration that asignal outputted from the first code production section 26, second codeproduction section 27 or third code production section 29 is supplied toa corresponding one of the first electrode 20 and the second electrode21, the supplying configuration is not limited to this specificconfiguration. In particular, the signals can be added through resistorsor the like and supplied to the first electrode 20 or the secondelectrode 21. According to this configuration, the signal supplyingpoints to the first electrode 20 or the second electrode 21 can bereduced, and the configuration as a pointer can be simplified.

While, in the description of the embodiment and the modifications 1 to 7described above, an excitation signal is received from an excitationcoil of the sensor section to produce a driving voltage for theintegrated circuit in the pointer, the present invention is not limitedto this configuration, and a power supply such as, for example, a drycell may be provided inside the pointer.

The invention claimed is:
 1. A position detection apparatus, comprising:a pointer including a transmission signal production section, which isconfigured to produce a signal based on two predetermined codes that aretime-staggered but are partially overlapping timewise, whose binarysequences are identifiable thorough a correlation operation, wherein oneof the binary sequences is indicative of a start timing of a timedifference and the other of the binary sequences is indicative of an endtiming of the time difference, and wherein the time difference isintroduced between the two codes that is indicative of a variablepressure applied to said pointer by controlling production timings ofsaid two binary sequences, the pointer being configured to transmit thesignal produced by said transmission signal production section; a sensorsection including a plurality of first conductors disposed in apredetermined direction and a plurality of second conductors disposed ina direction crossing with the predetermined direction and configured toreceive the signal transmitted from said pointer; a correlationoperation circuit configured to carry out a correlation operationbetween signals generated in conductors which form the plurality offirst conductors and conductors which form the plurality of secondconductors and predetermined correlation calculation codes correspondingto the two codes; a position calculation circuit configured to detect aposition on said sensor section pointed to by said pointer, based on aresult of the correlation operation calculated by said correlationoperation circuit and based on at least one of the two codes; and apressure calculation circuit configured to detect the pressure appliedto the pointer in accordance with the time difference between the twocodes, based on the result of the correlation operation calculated bysaid correlation operation circuit and based on the two codes.
 2. Theposition detection apparatus according to claim 1, further comprising aselection circuit configured to select a conductor in a predeterminedprocedure from among the plurality of first conductors and select aconductor in a predetermined procedure from among the plurality secondconductors, wherein signals generated in the conductors selected by saidselection circuit are supplied to said correlation operation circuit. 3.The position detection apparatus according to claim 1, wherein the twocodes have the same code pattern.
 4. The position detection apparatusaccording to claim 1, wherein the two codes have code patterns differentfrom each other.
 5. The position detection apparatus according to claim1, wherein said transmission signal production section includes amodulation circuit for modulating the codes, further comprising ademodulation circuit for demodulating signals generated in theconductors which form the plurality of first conductors and theconductors which form the plurality of second conductors.
 6. Theposition detection apparatus according to claim 1, wherein said pointerhas a projecting end portion and a pressure detection element configuredto detect a pressure applied to the end portion, and wherein the timedifference between the codes is set in response to a signal detected bysaid pressure detection element.
 7. The position detection apparatusaccording to claim 6, wherein said pressure detection element includes avariable capacitor having a capacitance, which varies when said variablecapacitor is pressed in response to the pressure applied to the endportion, and the time difference between the codes is controlled inresponse to a capacitance variation of said variable capacitor.
 8. Theposition detection apparatus according to claim 1, wherein said sensorsection includes an excitation coil, and said pointer includes a powerproduction circuit for receiving an excitation signal signaled from saidexcitation coil to produce power for driving said transmission signalproduction section provided in said pointer.
 9. The position detectionapparatus according to claim 1, wherein a hovering state and a pen downstate of said pointer can be identified in response to pressure detectedby said pressure calculation circuit.
 10. The position detectionapparatus according to claim 1, wherein the two codes have code patternsdifferent from each other, and a hovering state and a pen down state ofsaid pointer can be identified by detecting that a code is changed fromone code to another code based on a result of the correlation operationobtained by supplying the signal transmitted from said pointer to saidcorrelation operation circuit.
 11. The position detection apparatusaccording to claim 1, wherein an operation switch is provided on a sideface of said pointer, and a code inversion circuit configured to invertthe codes in response to an operation of said operation switch isprovided in said pointer, and a correlation operation of an invertedcode signal generated in response to the operation of said operationswitch is carried out by said correlation operation circuit to therebyallow detection of the operation of said operation switch.
 12. Theposition detection apparatus according to claim 1, wherein an operationswitch is provided on a side face of said pointer and, when a signalbased on a code corresponding to the operation of said operation switchis produced by said transmission signal production section, acorrelation operation of the code produced in response to the operationof said operation switch is carried out by said correlation operationcircuit to thereby allow detection of the operation of said operationswitch.
 13. The position detection apparatus according to claim 1,wherein the pointer comprises an end portion used for detection of apointed position and a pressure applied to said pointer projecting froma housing of said pointer, wherein said end portion has conductivitysuch that a signal produced by said transmission signal productionsection is transmitted through said end portion.
 14. The positiondetection apparatus according to claim 1, further comprising a codeproduction section configured to produce a predetermined code, and afirst changeover section configured to carry out changeover between asupplying process of supplying the code produced by said code productionsection to the plurality of first conductors disposed in thepredetermined direction and a reception process of receiving the signalsgenerated in the plurality of first conductors disposed in thepredetermined direction, wherein changeover control between thesupplying process and the reception process is carried out alternatelyby said first changeover section to detect a position on said sensorsection pointed to by a second pointer which is different in type fromsaid pointer.
 15. The position detection apparatus according to claim14, further comprising a second changeover section configured to carryout changeover between a signal generated in a first conductor disposedin the predetermined direction and outputted from said first changeoversection and another signal generated in a second conductor disposed in adirection crossing with the predetermined direction, time-divisionally,to supply the signals to said correlation operation circuit.
 16. Theposition detection apparatus according to claim 14, wherein the codeproduced by said code production section is different from either of thetwo codes produced by the transmission signal production section of saidpointer of claim
 1. 17. The position detection apparatus according toclaim 1, wherein a plurality of electrode pieces respectivelycorresponding to a plurality of signals produced by said transmissionsignal production section are disposed in said pointer in order totransmit the plurality of signals, and the signals are transmittedrespectively through said plurality of electrode pieces to be receivedby said sensor section for detecting an operation state of said pointer.18. The position detection apparatus according to claim 17, wherein theoperation state of said pointer to be detected is at least one of arotational state of said pointer around a pen tip axis thereof, aninclination of said pointer with respect to a plane formed by saidsensor section, and a rotational angle of said pointer projected to theplane formed by said sensor section where said pointer is operated withits pen tip as a reference point.
 19. A pointer having an end portion,which projects from a housing for pointing to a position, the pointercomprising: (a) a transmission signal production section configured to:(i) produce two codes, whose binary sequences are identifiable through acorrelation operation, wherein one of the binary sequences is indicativeof a start timing of a time difference, and the other of the binarysequences is indicative of an end timing of the time difference; and(ii) control production timings of said two binary sequences so as tointroduce the time difference between the two codes that is indicativeof a variable pressure applied to said end portion; and (b) atransmission signal output section configured to output the codesincluding the binary sequences produced by said transmission signalproduction section in a time-staggered but partially overlapping manner.20. The pointer according to claim 19, wherein the two codes have thesame code pattern.
 21. The pointer according to claim 19, wherein thetwo codes have code patterns different from each other.
 22. The pointeraccording to claim 19, wherein said transmission signal productionsection includes a modulation circuit for modulating the codes.
 23. Thepointer according to claim 19, further comprising a pressure detectionelement configured to detect a pressure applied to said end portion,wherein the time difference between the codes is set in response to asignal detected by said pressure detection element.
 24. The pointeraccording to claim 23, wherein said pressure detection element is avariable capacitor having a capacitance which varies when said variablecapacitor is pressed in response to the pressure applied to said endportion, and the time difference between the codes is controlled inresponse to a capacitance variation of said variable capacitor.
 25. Thepointer according to claim 19, further comprising an operation switchprovided on a side face of said pointer, and a code inversion circuitconfigured to invert the codes in response to an operation of saidoperation switch.
 26. The pointer according to claim 19, furthercomprising an operation switch provided on a side face of said pointer,wherein a code corresponding to the operation of said operation switchis produced by said transmission signal production section.
 27. Thepointer according to claim 19, wherein said end portion for pointing toa position has conductivity such that at least one code produced by saidtransmission signal production section is transmitted through said endportion.
 28. The pointer according to claim 27, wherein a plurality ofcodes produced by said transmission signal production section arerespectively transmitted through said end portion.
 29. The pointeraccording to claim 19, wherein a plurality of electrode pieces that areconfigured to respectively transmit a plurality of codes produced bysaid transmission signal production section are disposed in theproximity of said end portion.
 30. A position detection method,comprising: a code transmission step for transmitting two predeterminedcodes in a time-staggered but partially overlapping manner, whose binarysequences are identifiable through a correlation operation and arehaving a time difference therebetween which corresponds to a variablepressure applied to a pen tip provided on a pointer for positionpointing, the time difference being defined by a start timing indicatedby one of the binary sequences and an end timing indicated by the otherof the binary sequences, and the time difference being introduced bycontrolling production timings of the two binary sequences; a signalreception step for receiving the codes transmitted from the pointer witha plurality of first conductors disposed in a predetermined directionand a plurality of second conductors disposed in a direction crossingwith the predetermined direction; a correlation operation processingstep for receiving signals generated in conductors which form theplurality of first conductors and conductors which form the plurality ofsecond conductors, and carrying out a correlation operation between thereceived signals and predetermined correlation calculation codescorresponding to the two codes; a position calculation step fordetecting a position on a sensor section pointed to by the pointer froma result of the correlation operation calculated in the correlationoperation processing step and based on one of the two codes; and apressure calculation step for detecting pressure applied to the pointerfrom the result of the correlation operation calculated in thecorrelation operation processing step and based on the two codes. 31.The position detection method according to claim 30, wherein the twocodes have the same code pattern.
 32. The position detection methodaccording to claim 30, wherein the two codes have code patternsdifferent from each other.
 33. A pressure information transmissionmethod, wherein two codes, whose binary sequences are identifiablethrough a correlation operation, are transmitted in a time-staggered butpartially overlapping manner such that a time difference therebetween isassociated with a variable pressure applied to a projecting end portionof a pointer for pointing to a position, wherein said time difference isdefined by a start timing indicated by one of the binary sequences andan end timing indicated by the other of the binary sequences, whereinsaid time difference is introduced between said two codes by controllingproduction timings of said two binary sequences, and wherein thetransmitted codes including the binary sequences are subjected to thecorrelation operation for determination of both a position of thepointer and the pressure applied to the projecting end portion of thepointer.
 34. A pointer signal transmission method used in a pointer,comprising: a code production step for producing two codes in atime-staggered but partially overlapping manner, whose binary sequencesare identifiable through a correlation operation, wherein one of thebinary sequences is indicative of a start timing of a time differenceand the other of the binary sequences is indicative of an end timing ofthe time difference, and wherein the time difference is indicative of avariable pressure applied to said pointer and is introduced between saidtwo codes by controlling production timings of said two binarysequences; a step for supplying the two codes respectively tocorresponding ones of two electrode pieces electrically separated fromeach other; and a step for transmitting the two codes from thecorresponding ones of the two electrode pieces to be subjected to thecorrelation operation for determination of a position of the pointer.